(1) Field of the Invention
The invention relates to a direct type backlight module of a Liquid Crystal Display (LCD), and more particularly to a supporting unit of the direct type backlight module.
(2) Description of the Prior Art
Liquid Crystal Display (LCD), is well known to be applied to portable electronic products such as notebook PCs, cell phones, digital cameras, digital video machines and Personal Digital Assistants (PDA). Recently, maturity in techniques of making larger sized LCD has affected the market of display products quite a lot. For example, the desktop-typed LCDs are replacing the traditional CRT monitors. The LCD TV takes advantage of its thinness and lightness to compete with the traditional TV product. Within an LCD, the liquid crystal panel (usually “panel” for short) is an elementary element of the whole device. For the liquid crystal panel does not generate light itself, a back light source is needed for providing light to the panel. Larger sized LCD, about 20″ and larger, usually adopts direct type backlight module as its back light source.
Please refer to FIG. 1. It illustrates a cross section view of a panel and a direct type backlight module. As described above, the panel 10 does not generate light itself. So, a direct type backlight module 2 is disposed under the panel 10 so as to allow a user to see images presented by the panel 10.
The direct type backlight module 2 comprises a back bezel 22, a plurality of lamps 24 and a diffusion plate 26. The back bezel 22 comprises a substrate 221 and sidewalls 223 extending upward from margin areas of the substrate 221. The diffusion plate 26 is disposed on top of the sidewalls 223 and maintains a predetermined distance from the substrate 221. The plurality of lamps 24 is disposed between the diffusion plate 26 and the substrate 221. Each lamp 24 is arranged in a predetermined distance from each other. A light-reflecting material or a reflection sheet 28 is usually applied or disposed on the substrate 221 so as to enhance light-utilizing efficiency of the direct type backlight module 2.
However, some problems are accompanied with making larger sized LCDs. When the panel 10 and the direct type backlight module 2 become larger, a larger diffusion plate 26 is definitely needed. For the diffusion plate 26 is disposed on top of the sidewalls 223 and thus is only supported by the margin areas of the diffusion plate 26, the broader and heavier diffusion plate 26 would make itself bending to a convex shape. Such a bending of the diffusion plate 26 would change its original optical design and degrade the light uniformity. Besides, assembly quality between sidewalls 223 and diffusion plate 26 may also be reduced because of the bending of the diffusion plate 26.
For the situations described above, a plurality of supporting elements is then adopted between the diffusion plate 26 and the substrate 221 of the back bezel 22 to enhance the assembly quality of the direct type backlight module 2. Typical prior arts about those supporting elements are described below.
Please refer to FIG. 2. FIG. 2 illustrates a cross section view of a typical supporting element. Generally, the supporting element 3 is used as a cone shape, so also called as a “supporting cone”. The cone-shaped supporting element 3 has a top end with a smaller cross-section diameter L1 and a bottom end with a larger cross-section diameter L2. The rounded top end of the element 3 would point-contact with the diffusion plate 26 to avoid substantially light to enter the diffusion plate 26 through the contact area; i.e., to prevent an obvious “dark point” occurred in the direct type backlight module 2. However, to have the supporting element 3 screw-fastened to the substrate 221, the bottom end with a larger cross-section diameter L2 cannot be waived.
However, the prior art described above with FIG. 2 involves human labor in assembling the supporting element 3 by the screw 32. Thus, cost and production are limited due to its less-automation.
Please refer to FIG. 3. FIG. 3 illustrates a cross section view of another prior supporting cone. Similar to FIG. 2, the supporting cone 404 has a top end with a smaller cross-section diameter L1 and a bottom end with a larger cross-section diameter L3. In this case, the supporting cone 4 further comprises a column 402, a spring 404 and an anchor 406. The column 402 extends downward from the bottom end of supporting cone 4. The anchor 406 connects to the bottom of the column 402. The spring 404 surrounds the column 402. As shown in FIG. 3, the spring 404 and the anchor 406 are separately located at the different sides of the substrate 221 so as to clip the substrate 221 in between. A retainer ring 402 could also be adopted at the anchor 406 side to enhance the clipping performance. Thanks to a suitable configuration design as shown, the anchor 406 can be forced to deformed to pass through the hole of the substrate 221 during the mounting.
Although the prior supporting cone 4 shown in FIG. 3 is much easier to be assembled. However, the spring 404 limits its supporting ability. When an external force larger than the elastic force of the spring 404 is applied to the diffusion plate 26, the supporting cone 4 may slide within a predetermined distance (symbol “d” in FIG. 3). Yet, once the spring 404 is fatigue, the supporting tolerance may be lost.
Hence, how to improve the assembly process of the supporting cone easier and how to enhance the supporting ability in the direct type backlight module are important in achieving quality assembly of the module.